From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E57E9C2D0E4 for ; Tue, 24 Nov 2020 09:42:27 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BA2C92073C for ; Tue, 24 Nov 2020 09:42:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=virtuozzo.com header.i=@virtuozzo.com header.b="ev0tXi63" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA2C92073C Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33554 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1khUq9-0001az-Al for qemu-devel@archiver.kernel.org; Tue, 24 Nov 2020 04:42:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47896) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1khUnp-0000pC-TK; Tue, 24 Nov 2020 04:40:02 -0500 Received: from mail-eopbgr70115.outbound.protection.outlook.com ([40.107.7.115]:9853 helo=EUR04-HE1-obe.outbound.protection.outlook.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1khUnm-0002yZ-P1; Tue, 24 Nov 2020 04:40:00 -0500 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=NDGVPccxyLZ4J8fW3/CEnDXYJfLlTclJOnE+nX00G6ul+GOfgASPTlyVfYN060G/4dr4pwozBXYX7QKs4A4sX8UpRbM2uB3Dh6bfGBczNvijcxgEMvSzmgDAH3CT0hfJwCE7Fu9fvJp83OvmWx3NQvMQqXYf5U5wSNv8sNEf/QTnQPQj+2RWzk5CAlfWPw3ZnXd8YCmZnYfZ7TmuNe8TKL2kybIAinUrryfEd5IKv1a9FB7d51nOJZMV1r955GHDLIfLbmeGkURcmlEaMWT8/diqxL2uVEuC9oMvCaffZD+0Bh7mbJU9Y6/eY0VATT8JMHtBl5XBTpD2e7udOp7oQg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=x7E8tw81tt+AYZ531S++cLKritENuBXMrxjqAykoIAw=; b=F+cZiSUMrC+B7UwZ/BKCiD75fT3XqGCa/uiCTed9jJmYu99AHSD/4t0nSrxEM2WDMOko05iy9Rrw//v9OqL25FTxheNKKVNm94Ix4i1R4a87cQ5WL+wyO+Th3bEpppMUon6AbTVZVxRXL+vYW1dUAHJnLcWuesvjLV/SbShMBHCYZhmZLF/DWU5GCyS9OrnyA1HSmQGDcJrTB8b65tXa9RZtS8KRsYYcMXGaFAdT6Z4MRmmYj4DQcH8PFeFm4QY8Dq+HKTLKO2OlxpGr1xtV1dHC796hhN0V/NcKlO9UQgOAgeDbInSN9l/0ibZgleUu2gmKCQgD0Oq9oCCb7j0qIw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=virtuozzo.com; dmarc=pass action=none header.from=virtuozzo.com; dkim=pass header.d=virtuozzo.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=virtuozzo.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=x7E8tw81tt+AYZ531S++cLKritENuBXMrxjqAykoIAw=; b=ev0tXi63tHEs82F8wbdyDrpsVBQoKuiw8rVJajNvvH9pRCXsFhIyvSFFEkEQRbJCfcRQIhh8qZLhprcYIRXuQ2z1hkXZB5w4N49zk+iI5wdHSR+JWmpNR0Xp6FBJis0E4xiUL+yWd6q7M0g+gVa/+dPvXVpGy5NTEoD86S2lnjM= Authentication-Results: openvz.org; dkim=none (message not signed) header.d=none;openvz.org; dmarc=none action=none header.from=virtuozzo.com; Received: from AM7PR08MB5494.eurprd08.prod.outlook.com (2603:10a6:20b:dc::15) by AM6PR08MB4951.eurprd08.prod.outlook.com (2603:10a6:20b:eb::29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3589.29; Tue, 24 Nov 2020 09:39:54 +0000 Received: from AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::fd02:1330:f620:1243]) by AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::fd02:1330:f620:1243%9]) with mapi id 15.20.3589.030; Tue, 24 Nov 2020 09:39:53 +0000 Subject: Re: [PATCH 1/2] block: make bdrv_drop_intermediate() less wrong To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, armbru@redhat.com, jsnow@redhat.com, mreitz@redhat.com, kwolf@redhat.com, den@openvz.org References: <20201123201233.9534-1-vsementsov@virtuozzo.com> <20201123201233.9534-2-vsementsov@virtuozzo.com> From: Vladimir Sementsov-Ogievskiy Message-ID: <2a272dc2-3fc6-368f-11ee-e126b448f13e@virtuozzo.com> Date: Tue, 24 Nov 2020 12:39:52 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 In-Reply-To: <20201123201233.9534-2-vsementsov@virtuozzo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [185.215.60.100] X-ClientProxiedBy: AM0PR02CA0084.eurprd02.prod.outlook.com (2603:10a6:208:154::25) To AM7PR08MB5494.eurprd08.prod.outlook.com (2603:10a6:20b:dc::15) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.100.5] (185.215.60.100) by AM0PR02CA0084.eurprd02.prod.outlook.com (2603:10a6:208:154::25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3611.20 via Frontend Transport; Tue, 24 Nov 2020 09:39:53 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: d2bda6ee-f73a-45de-ff30-08d8905ce596 X-MS-TrafficTypeDiagnostic: AM6PR08MB4951: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8882; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 1ciSyM71/EBdSGAQk0vFHp+jYqxXkOSQ3EqGD7kPwoJHQHi1aHcOsJYG/R1s9oLo95vd7K2Quid+dATF1fRNvpKsgcKhyJfn4AYJRqAnxw4EqAcoVSY7ldsrmomklXdYtmr668sSPm2HdUNzZ3I87SRVoQNoycExLS2I+mhe/XMXlcm4f4BASHT7VjEnGiZORmtiqmkzPJL7ByrEqxQJcX2kpOg2aUotBzxi7P+XfQ2lFgVdgDeyKsJwRzE0fqRkVNv2tb/JJg2jEDmxror14Skzoly/Cy5BOdCVR5+0z9JLCoj2p0EVI3PDu2wg8FVWh7o0cErREaRKTUhH0XzYbdnpECMPkJvphxE9Xm5ui1YrmjqpQRsvn5bwT435EBPi X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:AM7PR08MB5494.eurprd08.prod.outlook.com; PTR:; CAT:NONE; SFS:(4636009)(376002)(39840400004)(396003)(136003)(346002)(366004)(2906002)(83380400001)(2616005)(52116002)(36756003)(5660300002)(6486002)(86362001)(31686004)(66556008)(26005)(956004)(66476007)(66946007)(4326008)(316002)(16576012)(31696002)(6916009)(107886003)(186003)(478600001)(16526019)(8676002)(8936002)(43740500002); DIR:OUT; SFP:1102; X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-Network-Message-Id: d2bda6ee-f73a-45de-ff30-08d8905ce596 X-MS-Exchange-CrossTenant-AuthSource: AM7PR08MB5494.eurprd08.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Nov 2020 09:39:53.8225 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 5y3baBHMYlrQo/Rg8Nr6j6pPq98xAlqgJOKIQNwWyMpFxsQlRhbVp1pXaRoNZ33lzLev+wCYpGXZialIcP0NttRh6/uBFai2PlInqdsmM8w= X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB4951 Received-SPF: pass client-ip=40.107.7.115; envelope-from=vsementsov@virtuozzo.com; helo=EUR04-HE1-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 23.11.2020 23:12, Vladimir Sementsov-Ogievskiy wrote: > First, permission update loop tries to do iterations transactionally, > but the whole update is not transactional: nobody roll-back successful > loop iterations when some iteration fails. > > Second, in the iteration we have nested permission update: > c->klass->update_filename may point to bdrv_child_cb_update_filename() > which calls bdrv_backing_update_filename(), which may do node reopen to > RW. > > Permission update system is not prepared to nested updates, at least it > has intermediate permission-update state stored in BdrvChild > structures: has_backup_perm, backup_perm and backup_shared_perm. > > So, let's first do bdrv_replace_node() (which is more transactional > than open-coded update in bdrv_drop_intermediate()) and then call > update_filename() in separate. We still do not rollback changes in case > of update_filename() failure but it's not much worse than pre-patch > behavior. > > Signed-off-by: Vladimir Sementsov-Ogievskiy this is accidental patch, ignore it -- Best regards, Vladimir